If I have long-distance trade magic, it won't look like the "teleportation circle" spell. The spells in the book are examples of spells, biased towards adventuring magic.
Almost all high-level magic casting in my world involves consuming a scroll with the spell on it. Teleportation Circle is a 5th level spell, so each scroll is a Rare consumable magic item. 100 Common/500 Uncommon/5000 Rare/20000 Very Rare/100000 Legendary, and halving for consumables, a 365 day teleportation ritual is about a million gold piece investment.
Equipping a knight costs about 2000 gp, much of it not consumed. So we are talking enough gold to equip a medium sized army.
As I like having higher level magic be in the midst of being rediscovered (from archeology and original research), this would be a serious research project (because who knows if it would work!). Even people with access to existing teleportation circles (found in various ruins usually) wouldn't even know how you could make a stable new one. So some massive project based off a crazy idea, noticed after mathemagicians measured a flux effect from repeated casting of teleportation circle in the same spot, might have recently led to a permanent teleportation circle being forged at a magical research institute with deep pockets.
Then along comes a PC who can actually cast higher level magic without destroying the magical inscription they are using?! This changes everything!
So, what does it cost to use a teleportation circle? Well, the one that has been made in the back room of the museum of archeology will probably require having status with the archeologists, as the circle is intended for serious research purposes and not mentioned to outsiders so the Admirality (or heavens, the south seas trading company!) won't claim the building.
Meanwhile, the one unearthed at Drakevault is reserved for registered researchers, supply runs and military messages. You could probably find a reason why you'd qualify as a supply run if you greased the right palms.